Scientific Lectures. 71 



ducing seeds, produce little microscope spores. These are the Crjp- 

 togamoiis plants of the botanist. The whole vegetable kingdom is 

 divided into these two great classes. ISTow, taking first the Phsejio- 

 gams, we shall find three classes of them. We have, first, that gronp 

 of plants to which all om- trees and shrubs and the greater part of 

 our cultivated plants and weeds belong — the Exogens, which have a 

 distinct pith, and wood, and bark. This is the highest group, the 

 Exogens. Then we have a class in which there is no distinction of 

 wood and bark, represented in the tropical regions by the palms, and 

 in our climate by the grasses. These are the Endogens. And lastly, 

 we have a class in which the pith, bark, and wood are all composed 

 of similar material — the Gymuosperms, represented here by our 

 pines, and in the tropical regions by the Cycads. Thus the Phseno- 

 gams are divided into three groups, represented respectively by the 

 oak or maple tree, the palm tree, and the pine tree. In the Crypto- 

 gams we may also make a threefold division — the Acrogens, or ferns 

 and club-mosses ; the Anophytes, or the common mosses, and the 

 Thallophytes or lichens, fungi and seaweeds. Next let us see what 

 relation the primeval flora bears to those of modern times. Two 

 relations are possible. First, that the primeval flora may belong to 

 a different classification altogether; and second, which is the true 

 supposition, that the whole fiora of the earth, from the earliest geo- 

 logic times, comes under one classification. This shows that, from 

 the beginrling of geologic time, one plan has been followed out in 

 the construction of the vegetable kingdom, and that the whole vege- 

 table kingdom consists not of the plants now living upon the earth, 

 but includes all the plants that have ever lived upon it. Again, 

 there is another possibility, that the primitive flora may include rep- 

 resentatives of all our modern classes of plants, or only some of 

 them. The fact is, that it includes mainly representatives of some 

 of them, and those of a medium grade, neither the lowest nor the 

 highest, so far as the land flora are concerned. The fossil plants are 

 not chiefly Exogens or Endogens, but Gymnosperms. On the other 

 hand the Acrogens, or the highest group of the cryptogamous plants 

 in our day were then the most abundant. The primeval flora there- 

 fore embraced the higher Cryptogams and the lower Phaenogams. 

 If we had known nothing of vegetation but that manifested by the 

 primeval flora we should not have known the possibilities of the vege- 

 table kingdom, either in its highest ranks or its lowest ranks, but 

 only in the middle of the scale. iSText let us glance at the relations 



